Device for detecting the density of developer in an electrostatographic duplicator

ABSTRACT

A device for automatically detecting the density of a developer made of a mixture of iron filings and developing colored powder or toner, that is, strictly speaking, detecting the quantity of the toner per unit volume of iron filings.

United States Patent [72] Inventor Takeshi Abe Tokyo, Japan [21 Appl. No. 714,230

[22] Filed Mar. 19, 1968 [45] Patented Jan. 5, 1971 [73] Assignee Kabushiki Kaisha Ricoh Tokyo, Japan [32] Priority Mar. 27, 1967 [33] Japan [54] DEVICE FOR DETECTING THE DENSITY OF DEVELOPER IN AN ELECTROSTATOGRAPHIC DUPLICATOR 2 Claims, 4 Drawing Figs.

[52] U.S.Cl 250/219, 118/637,356/20l [51] Int. Cl G0ln 5/02 [50] Field ofSeai-ch 118/637, 638,639; 356/201,202, 161-,222/57; 195/1.7; 250/219F, 219Th [56] References Cited UNITED STATES PATENTS 2,956,487 10/1960 Giaimo, Jr 95/1.7 3,348,523 10/1967 Davidson et al. 118/637X 2,710,574 7/1969 Runion 250/219 3,376,854 4/1968 Kamola 118/637 3,445,670 5/1969 Westdale 250/219 Primary Examiner-Walter Stolwein AttorneyWaters, Roditi, Schwartz & Nissen ABSTRACT: A device for automatically detecting the density of a developer made of a mixture of iron filings and developing colored powder or toner, that is, strictly speaking, detecting the quantity of the toner per unit volume of iron filings.

PATENTEU JAN 51am PRIOR ART DEVICE FOR DETECTING THE DENSITY OF DEVELOPER IN AN ELECTROSTATOGRAPI-IIC DUPLICATOR The present invention relates to a device for detecting the density of developer in an electrostatographic duplicator, especially, in an electrostatographic duplicator provided with a dry developing means.

In an electrostatographic duplicator, to obtain a clear visual image on a sheet of printing paper, the quantity of toner to be supplied to said printing paper must be of prescribed quantity. If not, i.e., if the toner is too little, the visual image will become faint, while if the toner is too great, it will not only make the ground of the printing paper dark but the details of the visual image will become obscure and unclear. It is extremely difficult to detect the density of developer in a dry developing means automatically because the developer is a powder, and is unlike detecting the density of liquid developer in a wet developing means. Therefore, no means for automatically detecting the density of developer in a dry developing means has been known heretofore.

It is an object of this invention to provide a device for automatically detecting the density of developer constituted of a mixture of iron filings and developing colored powder or toner, that is, strictly speaking, detecting the quantity of the toner per unit volume of said iron filings.

The detecting device of this invention comprises a tape which has the character of adhering toner thereto and which passes over said developing means, and means for measuring the quantity of the toner adhered to said tape.

To give the tape the character of adhering the toner thereto, it will either be possible to apply to a said tape charges of a polarity opposite to that of the toner by means of corona discharge or to supply weak adhesives to the tape, before the tape passes the developing means.

For a better understanding of this invention, reference is made to the following detailed disclosure of this invention taken in conjunction with the accompanying drawing wherein:

FIG. 1 is a sectional view of a known embodiment of a dry developing means in an electrostatographic duplicator;

FIG. 2 is a plan view of an embodiment of the present invention, including a device for detecting the density of the developer;

FIG. 3 is a sectional view taken along line 3-3 in P16. 2; and

FIG. 4 is a side view of another embodiment of this invention.

FIG. 1 shows an embodiment of a dry developing means already known. Reference number I denotes a tank filled with developer 2 made of a mixture of toner and iron filings. 3 is a fixed shaft penetrating through a number of magnets 4 so as to fix them. 5 denotes a developing roller which rotates around said magnets 4. 6 denotes an agitator which reciprocates the developer in the tank 1 in the direction of the shaft 3 of said developing roller 5 and serves for keeping the density of the developer in said tank 1 constant. 7 is a sheet of printing paper bearing an electrostatic latent image on its underside. The paper 7 is moved to the left in FIG. 1 and the surface of the printing paper 7 with the electrostatic latent image is brushed by a brush 2a with developer adhered to the circumferential surface of the developing roller 5 rotating in the direction shown by the arrow, so that a visual imagemay be obtained on said printing paper 7.

In FIGS. 2 and 3, a tape 8 extends in the direction of travel of the paper 7 and crosses an end part of said developing roller 5. The tape 8 is carried from a supply reel 9a to a takeup reel 9b. The tape 8 need not be transported continuously during the operation of the duplicator, but is stepwise transported in fixed lengths leftwards after a number of copies have been obtained.

The tape 8 is charged by a charging device 10 and is moved leftwards to contact the developer on the developing roller 5 and the toner is adhered to said tape 8. The quantity of the toner adhered to the tape 8 is detected by a light source 11 and a photoelectric converter element 12 facing each other throug the tape 8. A method of measuring light by its penetration through the tape can be employed and the quantity of the light which has passed through the tape 8 is measured, said tape being constituted of a material pervious to light. Alternately, a method of measuring the light by reflection can be employed in which case the surface of the tape material is reflective.

The electric variation obtained by the photoelectric converter element 12 is indicated by a meter so that the density of the toner may be known by reading said meter. Said electric variation may also be used to operate a device for automatically providing toner, and the toner is supplied automatically when the quantity of toner becomes less than a fixed quantity.

FIG. 4 denotes another embodiment of the device for detecting the density wherein an endless tape 18 running around a pair of pulleys 19a and 19b is used and when said tape 18 travels leftwards through the developing means D, the light source 11 and the photoelectric converter element 12, toner adhered to said tape 18 is scraped off by a toner removing plate 20 with its end pressed against the tape 18.

According to the device of this invention, it is possible to detect the quantity of toner in the dry developing means easily and certainly. Further, whenever the present invention is applied to an electrostatographic duplicator, a clear toner image can be obtained.

1 claim:

1. A device for detecting the density of a developer in an electrostatographic duplicator, said device comprising a developer means which comprises a tank containing a developer constituted of a mixture of toner and iron filings, and a rotatable developing roller mounted in said tank; an endless tape extending adjacent said tank and in contact with the periphery of said roller, said tape being capable of adhering said toner thereto; a pair of spaced pulleys supporting said endless tape for advancing said tape past said developing roller; a light source and a photoelectric converter element adjacent said tape for detecting the amount of toner adhered to said tape; means for electrostatically charging said tape with a polarity opposite that of said toner to attract the same from the developing roller; and means for scraping the toner from said tape after the tape has passed through the light source and photoelectric converter.

2. A device as claimed in claim 1 wherein said means for scraping the toner from said tape comprises a plate. 

2. A device as claimed in claim 1 wherein said means for scraping the toner from said tape comprises a plate. 